There are many reasons why the ability to control the contrast characteristics of a subject image at the time of image capture is desirable, on both a technical as well as an aesthetic level. There has been many endeavours to control or modulate the contrast characteristics of a live subject image during image capture in a recording device. Liquid crystal filters have been described for modulating the subject image to reduce contrast and improve pick-up quality for example in JP 2-1832 (MATSUSHITA) and GB 2,255,465 (SONY). These patents describe multiplexed signal addressing of a filter matrix, and largely concentrate on the use of a beam splitting prism or partial mirror directing a sample subject image onto a separate sensor array to pick up a drive signal.
Although proposing an effective contrast modulating systems for a camera, the systems described in these prior art patents have several practical limitations. For example, the use of beam splitters or partial mirrors limits the amount of light which can reach a recording or viewing medium. Additionally, as it is only the portion of the light reflected by the prism or partial mirror which is acted upon by sensors, rather than the whole amount of available light, the overall system sensitivity and fidelity is reduced. A further disadvantage is the bulk, voltage requirement and overall expense of these systems.
As a result of the above disadvantages, to this day, systems such as those referred to above, do not appear to have gained commercial acceptance nor wide practical use.